MORPHOLOGICAL PART. ke 
part consists of small limestone particles, or irregular plates, and was evi- 
dently flexible; while the conical part, which is composed of larger pieces, 
appears to be almost rigid. Nothing is said about ambulacra, which were 
probably not visible in the specimen. That the cone represents a short 
ventral sac, and that the affinities of the Encrinidx are with the Fistulata, 
and not with the Apiocrinide and other Neozoic Crinoids as heretofore, 
supposed by Miller, Miiller, Zittel and Carpenter, is clearly shown from 
Wagner’s description. 
Among Apiocrinidx de Loriol observed the tegmen in Apiocrinus roissy- 
anus,* a species with large, massive plates interposed between the rays, and 
in which the plates of the cup gradually pass into the tegmen, which consists 
of rather heavy plates. The interbrachial plates were regarded by Carpenter 
as “calyx” interradials, i. e. homologous with the interbrachials of the Acti- 
nocrinide, the plates of the tegmen, however, as “disk” plates, — a position 
which was controverted by us.t We asserted that if those plates were 
interradials, they should be followed by a “vault;” but if the 
“calyx” 
tegmen was a disk, then the plates between the rays also had to be con- 
sidered as disk plates. We came to this conclusion upon ascertaining that 
the plates of the tegmen form a continuation or extension of those in the 
cup. The plates of the two hemispheres in most cases pass imperceptibly 
from one into the other, and have the most intimate relations. 
Apiocrinus is not the only Neocrinoid genus as to which there have been 
doubts respecting the homologies of the interbrachial plates. Guettardicrinus 
is morphologically in exactly the same condition, and the recent genus Thau- 
matocrinus has five large plates interposed between the radials, resting upon 
the basals, and followed by very minute, irregular pieces, which eradually 
pass into the tegmen. Also in many of the Ichthyocrinide the plates be- 
tween the rays are large and heavy; while those of the tegmen are ill-formed 
and unusually small. Glyptocrinus has minute, irregular pieces in the teg- 
men, and well defined and regularly arranged plates in the cup. In all these 
cases Carpenter took the larger plates to be “ calyx interradials,” but called 
the others “disk plates,” although the former occupy relatively the same 
position as the smaller ones, and as the disk plates of the Comatule, Calamo- 
erinus, and the Pentacrinide. Our recent studies show plainly that neither 
the condition of these plates, nor the presence or absence of the ambulacra 
* Paléont. Frang., lre série; Anim. Invert., Crinoides, p. 272. 
+ Revision, Part III., pp. 63, 72, and 137. 
